From LoveToKnow 1911

ANTICLIMAX (i.e. the opposite to "climax"), in
rhetoric, an abrupt
declension (either deliberate or unintended) on the part of a speaker or writer from the
dignity of idea which he appeared to be aiming at; as in the
following well-known distich: "The great Dalhousie, he, the god of
war, Lieutenant-colonel to the earl of Mar." An anticlimax
can be intentionally employed only for a jocular or satiric
purpose. It frequently partakes of the nature of antithesis, as "Die and
endow a college or a cat." It is often difficult to
distinguish between "anticlimax" and "bathos"; but the former is more decidedly a
relative term. A whole speech may never rise above the level of
bathos; but a climax of greater or less elevation is the necessary
antecedent of an anticlimax.